1. Field of the Invention
The present invention relates to a clamping apparatus of such a type that pulls an output rod.
2. Explanation of Related Art
U.S. Pat. No. 4,488,713 disclosed a conventional example of the clamping apparatus of this type.
The conventional technique forms a pneumatic chamber below a piston. When clamping, it pulls an output rod through the piston with compressed air supplied to the pneumatic chamber. And when unclamping, it returns the output rod through the piston by a compression spring.
The conventional technique had a problem that it produces only a small clamping force because the compressed air which is utilized as working fluid has a low pressure.
The present invention has an object to provide a clamping apparatus which can produce a strong clamping force.
In order to accomplish the above-mentioned object, the present invention has constructed a clamping apparatus in the following manner, for example, as shown in FIGS. 1 to 9, FIG. 10 or FIG. 11.
An annular piston 20 is axially movably and hermetically inserted into a cylinder portion 13. A first chamber 21 is formed between a first end wall 15 of the cylinder portion 13 and the piston 20. A second chamber 22 is formed between a second end wall 16 of the cylinder portion 13 and the piston 20. An output rod 26 is provided substantially concentrically with the piston 20. The output rod 26 is axially movably and hermetically inserted into the second end wall 16. Within the second chamber 22, a first pressure receiving member 31 and a second pressure receiving member 32 axially oppose to each other in an annular space defined between the piston 20 and the output rod 26. An annular engaging space 33 is formed between the first pressure receiving member 31 and the second pressure receiving member 32 so that it narrows radially inwards. A plurality of engaging members 34 are inserted into the engaging space 33 and spaced apart from each other peripherally at a predetermined interval. The first pressure receiving member 31 and the second pressure receiving member 32 are connected to a first end 26a of the output rod 26 and to the second end wall 16, respectively. A driving means 47 provided in the first chamber 21 drives the piston 20 toward the second end wall 16, thereby enabling a push surface 37 provided on the piston 20 to drive means the output rod 26 toward the first end wall 15 through the engaging members 34 and the first pressure receiving member 31 in the mentioned order. On the other hand, when pressurized fluid is supplied to the second chamber 22, the pressurized fluid drives the piston 20 to return it toward the first end wall 15 and the output rod 26 to return it toward the second end wall 16.
As for the driving: means 47, it is considered to utilize at least one of a pressurizing force of pressurized fluid which is supplied to the first chamber 21 and an urging force of a spring 25 attached to the first chamber 21.
Further, as for a clamp member which is connected to a second end 26b of the output rod 26, it is considered to use a clamp arm 10 in FIG. 2 and a T-leg 7 in FIG. 11.
The present invention functions in the following manner, for example, as shown in FIGS. 2 and 3.
Under an unclamping condition shown in FIG. 2, compressed air or the like pressurized fluid is supplied to the second chamber 22. A pressure of the pressurized fluid moves the piston 20 toward the right which is the first end and the output rod 26 toward the left which is the second end. This moves the plurality of engaging members 34 radially outwards of the engaging space 33 and brings the first pressure receiving member 31 near the second pressure receiving member 32.
When switching over the unclamping condition of FIG. 2 to a clamping condition of FIG. 3, the pressurized fluid is discharged from the second chamber 22 and the driving means 47 moves the piston 20 toward the left which is the second end. Then the push surface 37 provided on the piston 20 moves the engaging members 34 radially inwards of the engaging space 33. This allows the first pressure receiving member 31 and the second pressure receiving member 32 to try to strongly separate from each other in a right and left direction by a wedging action of the engaging members 34. And the second end wall 16 of the cylinder portion 13 receives the second pressure receiving member 32, thereby enabling the first pressure receiving member 31 to pull the output rod 26 rightwards strongly.
In consequence, the present invention offers the following effect.
A driving force added from the driving means to the piston can be force-multiplicably converted and then transmitted to the output rod through the engaging members and the first pressure receiving member. Therefore, it is possible to strongly pull the output rod. This results in the possibility of strongly clamping a metal mold or the like objects to be fixed by the clamp member such as the clamp arm or the T-leg connected to the output rod.
Besides, when unclamping, the pressurized fluid which has been supplied to the second chamber can return not only the piston but also the output rod. Accordingly, it is possible to omit a return means intended exclusively for returning the output rod. This leads to the possibility of making the clamping apparatus compact with a simple structure.
The present invention includes the following clamping apparatus.
For example, as shown in FIG. 6 or FIG. 9, the engaging members 34 comprise balls, rollers or the like rolling members. In this case, it is possible to drive the engaging members smoothly by a small frictional force with the result of enhancing a transmission efficiency and eventually producing a larger clamping force.
The present invention further includes the following clamping apparatus.
For instance, as shown in FIGS. 2 and 3 or in FIG. 10, the cylinder portion:13 is fixed to a support block 6. The support block 6 swingably supports a fulcrum portion 10a of a clamp arm 10. A second end 26b of the output rod 26 is swingably connected to an input portion 10c of the clamp arm 10. In this case, it is possible to swing the clamp arm by an axial driving force of the output rod and therefore to provide a proper clamping apparatus depending on the kind of the metal mold or the like objects to be fixed.
The present invention furthermore includes the following clamping apparatus.
For example, as shown in FIGS. 2 and 3 or in FIG. 10, the cylinder portion 13 is detachably attached to the support block 6. In this case, the support block and the cylinder portion are made as separates parts. Thus the cylinder portion can be utilized for clamping apparatuses of different, types as a common part. This results in the possibility of manufacturing those clamping apparatuses at a low cost and besides facilitating maintenance.
The present invention still includes the following clamping apparatus.
For example, as shown in FIGS. 2 and 3 as well as in FIGS. 4A and 4B, the support block 6 has its lower portion provided with a T-leg 7 which engages with a T-groove 8 of a fixing pedestal 1 or a T-groove of a guide block attached to the fixing pedestal 1. The T-leg 7 is provided with a projection 7a which vertically faces an output portion 10b of the clamp arm 10. In this case, it is possible to vertically hold the metal mold or the like objects to be fixed: between the output portion of the clamp arm and the projection of the T-leg when clamping. This can prevent the support block from inclining by a clamp reaction force which occurs at that clamping time. In consequence, it is possible to decrease a swing angle of the clamp arm by an angle corresponding to the inclination of the support block. As a result, it is possible to reduce a stroke of the output rod and ultimately to make the clamping apparatus compact. In the event that at least one part of the driving means is composed of the pressurized fluid which is supplied to the first chamber, the pressurized fluid is consumed in a smaller amount owing to the fact that the stroke of the output rod is reduced. This can provide an energy saving clamping apparatus.
The present invention still includes the following clamping apparatus.
For example, as shown in FIG. 10, the support block 6 is detachably attached to a side surface (or an upper surface) of the fixing pedestal 1. In this case, the T-groove or the like need not be provided in the fixing pedestal. This makes the structure for attaching the clamping apparatus simple and reliable.
The present invention still more includes the following clamping apparatus.
For example, as shown in FIG. 5A, the push surface 37 of the piston 20 comprises an arcuate surface 38 and a tapered surface 39 formed in the mentioned order from the second end wall 16 toward the first end wall 15.